Device and system for filtering blood

ABSTRACT

Device ( 5 ) for filtering blood including a filter unit ( 7 ) having a blood filter, an inlet ( 8 ) for blood to be filtered and being connectable to an artery of a patient and a blood outlet ( 9 ) for filtered blood and being connectable to a vein of the patient, and having a filtrate container ( 6,14 ), that encloses the filter unit ( 7 ), for receiving filtrate ( 12 ) passing through the blood filter during a filtering process and that the filtrate container ( 6,14 ) is a closed container, which in a filled state is arranged to establish a counter-pressure over the blood filter, whereby the filtering process is interrupted. The invention also concerns a system including the above device.

FIELD OF THE INVENTION

The invention concerns a device for filtering blood according to thepreamble of claim 1. The invention also concerns a system for ultrafiltration of blood including such a device.

DESCRIPTION OF PRIOR ART

It is previously known to treat patients having chronic renal failurewith hemodialysis. Hemodialysis treatments are traditionally carried outabout three times a week, whereby the blood is purified and the liquidbalance is adjusted at a hemodialysis site in a hospital.

One condition for hemodialysis is the establishment of a connection tothe patient's bloodstream having a sufficience flow. This may beaccomplished by inserting catheters into the blood system or to use-animplanted bloodstream access device which may be connected to anartificial kidney. Such devices may be used repeatedly for numeroustreatments.

Since the kidneys of a patient suffering from renal conditions usuallydo not produce any urine, the patient normally turns up at thehemodialysis site with an excess of liquid in the body. After thehemodialysis treatment this has been changed to a shortage of liquid inthe body. These fluctuating fluid levels may cause serious healthproblems besides the conditions that the patients are treated for.

AIM AND MOST IMPORTANT FEATURES OF THE INVENTION

It is an aim of this invention to provide a solution to the aboveproblem and in particular to suggest a simple, economic and effectivesolution allowing better control of the liquid balance for dialysispatients having a chronic renal failure diagnosis.

This aim is achieved with a device according to the above through thefeatures of the characterising portion of claim 1.

This way it is possible to effectively filter out a desired,predetermined amount of liquid from the blood of the patient between theordinary hemodialysis treatments. This brings about great advantages forthe patients, since it provides important opportunities to bettercontrol the liquid balance between the treatments, whereby the liquidlevel is allowed to be equalised over time. This measure can radically reduce strain on the patient's body caused by fluctuating liquid levels.

The device is simple to make portable so as to be capable of beingconveniently used outside a dialysis site. Patients could thereforewithout any difficulty be trained to use it, for example, in the homes,and still be movable. This allows the patients to attend also to othertasks, such as cooking, cleaning etc., without being restricted to stayin bed or be tied to a specific, stationary apparatus for a substantialtime during the treatment. In particular, the provision of a filtratecontainer which encloses the filter unit simplifies production andhandling of the device as well as the process for its use in practice.

Providing a substantially rigid vessel for collecting filtrate andhaving an air vent therein, allows production and provision of a robustdevice which can be easily handled in virtually any environment.

Providing a flexible expandable container, which is collapsible in anempty state, as the filtrate container, simplifies transport; storageand related handling.

Production, handling and use is further enhanced when the devicecomprises an integral unit which is being disposable after use.

Further advantages are obtained with other aspects of the invention.Such aspects are subject to dependent claims and will become apparentfrom the following description of embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is now described in greater detail at the background of anembodiment and with reference to the annexed drawings, wherein:

FIG. 1 shows a system according to the invention carried by a patient,

FIG. 2 shows a device for filtering blood included in the system of FIG.1, and

FIGS. 3 and 4 show alternative embodiments of the device according tothe invention.

DESCRIPTION OF A PREFERRED EMBODIMENT

In FIG. 1 a dialysis patient 1 suffering from renal failure conditionscarries an implanted bloodstream access device 2 which is connected overconnection houses 3, 4 to a blood filtering device 5. The bloodstreamaccess device 2 is preferably an implanted device, as the one disclosedin WO 99/20338 (Danielson et. al.).

Such an access device is marketed under the trade mark Hemaport 605.That device provides a considerable pressure difference between theartery and the vein side so as to drive a continuous flow of bloodthrough an external circuit. Also other blood access devices providingsufficient pressure difference may be used together with the invention.

In this connection it could be mentioned that vascular grafts andfistulas which are commonly used for gaining access to a patient'sbloodstream do not provide sufficient pressure difference for drivingthe blood through a blood filtering device according to the invention.

In the case illustrated in FIG. 1, the blood filtering device includes arigid container which is carried by the patient 1 with the aid of afastening strap 16.

The blood filtering device 5 is shown in greater detail in FIG. 2. Herethe device 5 is shown including a filtrate container 6 which at itsupper portion contains a filter unit 7. The filter unit is comprised ofa substantially tubular, hollow ultra filtration filter having closedends in inlet and outlet regions of the filter unit 7. An inletconnection hose 4 is connected to an inlet nipple 8 leading in to theinterior of the filter unit 7.

At the outlet end of the filter unit 7, an outlet nipple 9 connects withan outlet connection hose 3. The inlet and outlet connection hoses 4 and3 are connected to the respective artery and vein side of thebloodstream access device 2 (FIG. 1). The inlet and outlet nipples 8, 9also contribute to positioning the filter unit 7 with respect to thefiltrate container 6 by being engaged in through-holes (not shown) inthe wall of the container.

In use of the device 5, blood flows from inlet nipple 8 through thefilter unit 7, where a portion of the liquid component of the blood isfiltered out as filtrate through the filter wall of the filter unit 7 soas to be collected inside the filtrate container 6. The remainingcomponents of the blood are discharged through the outlet nipple 9 overthe connection hose 3 so as to be brought back into the bloodstream ofthe patient over the bloodstream access device 2 (FIG. 1).

The properties of the filter of the filter unit 7 is chosen in such away that an appropriate amount of said liquid component is filtered outas filtrate. This could be easily tested for for example ultrafiltration filters and choosing a suitable filter area for chosenmaterial properties so as to apply to certain conditions andapplications of use. One example of a condition to consider is the bodyweight of a patient.

In case the filtrate container 6 is a rigid or semi-rigid container, gasor air being present inside the filtrate container must be allowed toescape therefrom so as to leave room for the filtrate. For that reasonat least one air vent 10 is provided at an appropriate position at thetop region of the filtrate container 6.

Preferably the air vent 10 includes a membrane which is air or gaspermeable and liquid impermeable so that no liquid leakage will occurthrough the air vent 10 while gas may escape. Other solutions such asliquid controlled flap-valves or the like are also possible to use, inorder to allow air to escape from the filtrate container but liquid toremain inside.

The filtrate container 6 may come in different volumes, for examplehaving between 0.2 to 1 litre volume, depending on such conditions asfor example body weight of the patient and also which amount of liquidthat is desired to withdraw from the patient at the specific occasion.

Preferably the filtrate container 6 is at least translucent, allowing avisual indication of the level 13 of filtrate 12 inside the container.The container may also have a scale 11 readable against the filtratelevel 13.

According to the invention, when a desired amount of filtrate iswithdrawn from the bloodstream the filtrate container 6 will becompletely filled with that amount of filtrate. This will result in thatthe filtering operation of the filter unit 7 is interrupted because acounter-pressure will be established over the filter wall of the filterunit. This in turn results in that all blood entering the filter unit 7through the inlet nipple also will flow through the outlet nipple 9.From there it will be fed back into the bloodstream through the outletconnection hose 3 and the bloodstream access device 2 (FIG. 1).

As an alternative, it is possible that a counter-pressure over the bloodfilter will be established when the filtrate 12 reaches a filtrate levelover the air vent 10, thereby trapping air between the filtrate level 13and the filter unit 7. This may create a sufficient counter-pressureover the wall of the filter for the filter action be terminated.

In FIG. 3 a filtrate container 14 is shown being a flexible, collapsiblepouch type filtrate container. In this case a counter-pressure of amagnitude being sufficient for the filter action to be terminated willbe established when the pouch comprising the filtrate container 14reaches such an expanded state that further expansion is impossible withthe pressure available through the wall of the filter unit 7. Also inthis case the filter unit is placed inside the filtrate container 14.

FIG. 4 shows a further embodiment, wherein a filtrate container 14,substantially like the one described in connection with FIG. 3, iscontained inside a rigid outer container 15. That outer container 15must not be liquid tight but may only be intended to protect theflexible container and possibly to provide a volume restriction thereof.

It is highly preferred that all parts of the system for blood filteringare disposable after use, including the filtrate container, the filterunit, the connection hoses and also a connection lid which is intendedto co-operate with the blood-stream access device 2 (FIG. 1). Such aconnection lid may be of a kind described in the above mentioned WO99/20338.

Materials for use in elements comprising the invention must fulfilnormal requirements for medical purposes. Filter materials for use inthe filter units shall be of the kind normally used for filtration ofblood such as ultra filtration filters.

The invention is described for filtering a liquid component from apatient's blood. That liquid component may, however, include alsocertain solid substances.

1. Device for filtering blood including a filter unit having a bloodfilter, an inlet for blood to be filtered and being connectable to anartery of a patient and a blood outlet for filtered blood and beingconnectable to a vein of the patient, and having a filtrate containerfor receiving filtrate passing through the blood filter during afiltering process and that the filtrate container is a closed containerwhich in a filled state is arranged to establish a counter-pressure overthe blood filter, whereby the filtering process is interruptedcharacterized in that the filtrate container encloses the filter unit.2. Device according to claim 1, characterized in that the filtratecontainer includes a substantially rigid vessel for collecting filtrateand an air vent for allowing the escape of air from the vessel during afiltering process.
 3. Device according to claim 1, characterized in thatthe air vent comprises an air permeable, liquid non-permeable membrane.4. Device according to claim 1, characterized in that the filtratecontainer includes a flexible, expandable container which is collapsedin an empty state.
 5. Device according to claim 4, characterized in thatthe flexible, expandable container is enclosed in an outer,substantially rigid container.
 6. Device according to claim 1,characterized in that the filtrate container with the filter unitcomprises a one-way, disposable unit.
 7. Device according to claim 1,characterized in that the blood filter comprises a substantially tubularfilter body.
 8. Device according to claim 1, characterized in that theblood filter is an ultra filtration filter.
 9. Device according to claim1, characterized in that the filtrate volume of the filtrate containeris chosen between about 0.2-1 litre.
 10. System for ultra filtration ofblood including a device according to claim
 1. 11. System according toclaim 10 including an implanted bloodstream access device.
 12. A methodfor filtering blood of a patient, said method comprising the steps of:providing a blood filter having an inlet and an outlet, and a filtratecontainer enclosing said blood filter for receiving filtrate passingthrough the blood filter during a filtering process, the blood filterand the filtrate container being adapted to be worn by the patient;obtaining blood from the inlet which is adapted to be connected to anartery side of the patient; filtering of blood with the blood filteruntil a predetermined amount of filtrate has been obtained; andreturning the filtered blood to the outlet adapted to be connected to avein side of the patient; wherein the above steps are performed in orderto remove excess fluid from the blood stream of the patient.
 13. Themethod according to claim 12, wherein the filtrate container includes asubstantially rigid vessel for collecting filtrate and an air vent forallowing the escape of air from the vessel during the filtering process.14. The method according to claim 13, wherein the air vent comprises anair permeable, liquid non-permeable membrane.
 15. The method accordingto claim 12, wherein the filtrate container includes a flexible andexpandable container that is collapsed in an empty state.
 16. The methodaccording to claim 15, wherein the flexible and expandable container isenclosed in a substantially rigid outer container.
 17. The methodaccording to claim 12, wherein the blood filter comprises asubstantially tubular filter body.
 18. The method according to claim 12,wherein the blood filter is an ultra filtration filter.
 19. The methodaccording to claim 12, wherein the filtrate container has a filtrationvolume of about 0.2-1 litre.
 20. The method according to claim 12,wherein an implanted bloodstream access device is provided forconnecting with said inlet and outlet of the blood filter.
 21. Themethod according to claim 18, wherein the above steps are performed topartially replace the hemodialysis treatment.